$A$ thick current-carrying cable of radius $R$ carries current $I$ uniformly distributed across its cross-section. The variation of magnetic field $B(r)$ due to the cable with the distance $r$ from the axis of the cable is represented by:

The maximum magnetic field produced by a current of $12 \ A$ passing through a copper wire of diameter $1.2 \ mm$ is (in $mT$)

$A$ long,straight wire of radius $a$ carries a current distributed uniformly over its cross-section. The ratio of the magnetic fields due to the wire at distance $\frac{a}{3}$ and $2a$ respectively from the axis of the wire is

$A$ long copper tube of inner radius $R$ carries a current $i$. The magnetic field $B$ inside the tube is

Write the equation of magnetic field on the axis of a current-carrying finite solenoid.

$A$ solenoid of $1000$ turns per metre has a core of material with relative permeability $400$. The windings of the solenoid are insulated from the core and a current of $2 \ A$ is passed through the solenoid. Then the value of the magnetic intensity inside the solenoid is